Inverse regulation of Vibrio cholerae biofilm dispersal by polyamine signals

The global pathogen Vibrio cholerae undergoes cycles of biofilm formation and dispersal in the environment and the human host. Little is understood about biofilm dispersal. Here, we show that MbaA, a periplasmic polyamine sensor, and PotD1, a polyamine importer, regulate V. cholerae biofilm dispersal. Spermidine, a commonly produced polyamine, drives V. cholerae dispersal, whereas norspermidine, an uncommon polyamine produced by vibrios, inhibits dispersal. Spermidine and norspermidine differ by one methylene group. Both polyamines function to control dispersal via periplasmic detection by MbaA and subsequent signal relay. Biofilm dispersal fails in the absence of PotD1 because reuptake of endogenously produced norspermidine does not occur, so it accumulates in the periplasm where it stimulates MbaA. These results suggest that V. cholerae uses MbaA to monitor environmental polyamines, blends of which potentially provide information about numbers of self and other. This information is used to dictate whether or not to disperse from biofilms.